We intend to study the effects of alcohol ingestion on aircraft pilot performance. This study will become part of a large programmatic investigation of the effects of "recreational" drugs on pilot performance that includes both alcohol and marijuana abuse. Virtually no programmatic research has studied the course of alcohol's effects on pilot performance. This is surprising considering the fact that over 700 people have died in alcohol-related air crashes between 1975 and 1981 (10.1% of all crashes). While performance research shows significant cognitive and behavioral impairments related to the use of alcohol, the interaction of factors such as level of dose, the duration of drug effects, and task difficulty have not been studied with respect to pilot performance. Furthermore, these variables have not been examined in relation to such factors as alcohol usage patterns, level of fatigue, pilots' flying experience, and age of pilot. We plan to investigate these factors and their interactions in a series of four experiments. The independent and dependent variables studied in these experiments were selected on the basis of existing findings and their ecological validity. The dependent measures are collected on relevant flight performance measures. All four experiments share a subset of four independent variables: a) drug type, b) alcohol dose level, c) task difficulty, and d) delay period between alcohol dose and test. Experiment I asks what effects these four variables plus the pilots' level of recreational use of the drug have on performance. Experiment II asks what effects these four variables plus pilot fatigue have on performance. Experiment III asks what effects these four variables plus flying experimence have on performance. Experiment IV asks what effects these four variables plus age of pilot have on performance. In these experiments we will be particularly concerned with the possible interaction effects of two or more variables. The four experiments will be conducted over a three-year period using a flight simulator specifically developed for empirical research on the pilot performance. Through these experiments we intend to obtain basic knowledge about the effects of alcohol on pilot prerformance.